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Voltage supply for an old "zenith flyback" power board.

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killivolt

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I have an old Zenith Chassis 9-181-02. I'm showing 170vdc at the Main connector to the flyback board.

I have 2 other flyback boards that don't have a chassis to supply that voltage to them.

I want to just feed them the 170vdc and power them up. I'm thinking I will need a transformer that will supply that as well as at least 3amps, then I will rectify it and smooth it with a good capacitor.

Any other suggestions please.
 
I looked at the supply board feeding 170vdc, I found a 300uf cap @ 180wv I think this is a smoothing cap. I also found a power resistor 4ohm 10watt. just in front of a transformer.

I think it is just a isolation transformer because it was at the end of the line where I measured the 170vdc going to the HV board.

Here is what I think is happening as I trace the voltage back to the mains.

Mains>choke-coil>Step-up transformer>rectifier>300uf@180wv>4ohm/10watt?(Not sure if it's in the path, unless I pull the) last component the isolation transformer = 170vdc to supply the HV board.

Does anyone have a good idea or suggestions on the best way to get it as close to the supply board voltages. I don't know enough about Flyback circuits either, I don't know if it is necessary to supply the vertical and horizontal deflection along with b+ to maintain a good stable output from the HV and not saturate the core.

If someone knows this circuit or has a schematic I would greatly appreciate getting it. I'm hoping this is the internal chassis # 1-181-02 used by zenith to replace it. I don't know the model # of the unit.
 
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Good Luck, sorry I'm the wrong person to ask.

is it possible to replace a flyback of 21- inch tv set with that of smaller tv sets,say 14 in.?

Jeffery I'm no authority on TV Repair, most of the time when I worked on them I used a data base 10yrs ago which was build up by other Technicians.


My own assumption based on what little I know is that it would require a lot more power for the horizontal and vertical deflection. This would increase the power rating of the Transformer. In addition, I would think most company's build to spec; if they did increase the power rating they would have to put in additional components to compensate.

The first part of what said, is most likely accurate e.g. building to spec. The second as I'm not an Engineer, it is possible that if a transformer were over it's power rating that the set may only draw what it would need therefor, it would not require additional components.

But, I just don't see them doing that; I know you can increase power by using the right driver and capacitors but, that may saturate the Transformer very quickly with the day to day demand required by consumer electronics. I personally would say no.

Putting it in open forum is the best thing to do, if you want a correct answer with explainations; Nigel, most likely will be able to state all the facts clearly as he has worked in a repair shop for many yrs and understands the complexity of circuit design and function .

kv
 
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flyback transformers vary from model to model on most TVs. the bigger the tube, the higher the voltage required for the anode, and the more current required for the deflection yoke. focus element voltages and screen grid voltages also vary with tube size, and since these controls are built-in to most flybacks, a different voltage division ratio might be used internally. i'm not saying it won't work, what i'm saying is it might not work well. what you may find is that it works, but the picture is distorted horizontally,squished or stretched on one side or stretched in the middle and squished on both sides. the fact that yokes are glued to the tube is another possible source of trouble. the yoke from one tube might not be well matched to the primary inductance of a different flyback. it's the inductance of the yoke, along with other wave shaping components that take a rectangular pulse from the output transistor and flyback and turn it into a linear ramp of current through the yoke. the distorted pictures i described above are indications that the ramped current isn't linear. if you were to try swapping the old yoke on to the new tube, be prepared for several hours of convergence alignments. when i was repairing computer monitors i got the process down to a couple of hours. i can tell you it takes practice and preparation to get it right.
 
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